1. Field of the Invention
This invention relates generally to air pressure gauges for pneumatic tires and, more specifically, to an air pressure gauge assembly mounted to the valve stem of a tire for continuous monitoring of the tire inflation without interfering with the common function of a valve stem; and an air pressure gauge assembly permanently mounted to the rim of a wheel for continuous monitoring of the tire inflation.
2. Description of the Prior Art
Proper tire inflation is important for fuel economy of a vehicle and prolongs the life of a tire. By maintaining proper tire inflation, optimum performance of a vehicle can be reached while keeping the operating costs relatively low and the safety relatively high. Under inflation of a tire can cause excessive wear of the tire, tire failure, loss of fuel economy, excessive engine drag, increased emissions, and depletion of fossil fuels.
In general, the air pressure of a tire is checked by removing a cap from a valve stem, applying a pressure gauge to the valve stem to get a pressure reading, and replacing the cap onto the valve stem. In order to simplify this process several replacement valve caps have been developed, which indicate when the tire pressure falls below normal, for example U.S. Pat. No. 5,365,967 issued to Moore, U.S. Pat. No. 4,606,391 issued to Achterholt, and U.S. Pat. No. 5,040,562 issued to Achterholt. A lower then normal tire pressure is indicated by color codes or other indicator means. These devices only indicate a low tire pressure without displaying the real pressure of the tire. To inflate the tire, the valve cap still needs to be removed and the correct tire pressure needs to be determined after inflation with a traditional pencil gauge or other type of external gauge before the valve cap can be replaced.
Prior art also includes air pressure gauges mounted directly to a tire valve stem, for example U.S. Pat. No. 4,924,697 issued to Hunt et al., U.S. Pat. No. 5,377,539 issued to LaSalle, and U.S. Pat. No. 5,503,012 issued to Rabizadeh. Other air pressure gauges are directly substitutable for a conventional valve stem, for example U.S. Pat. No. 3,969,936 issued to Lindsay, but require the tire to be deflated for installation thereof. The prior art further includes air pressure gauges mounted to a gauge-securing threaded aperture typically provided in the wheel of a pneumatic tire for an aircraft, for example U.S. Pat. No. 4,248,080 issued to Chuck. All of these devices monitor and indicate the tire inflation pressure continuously. While some devices need to be removed for inflating the tires, others do not interfere with the tire inflation through the valve stem and also monitor the air pressure while inflating the tire. Still most of these air pressure gauges are connected to the tire valve stem and are driven by the air coming through the valve stem. This can cause a problem when replacing the tire and/or the valve stem. Also, if a prior art pressure gauge is accidentally broken off or fractured, air may leak causing hazardous deflation of the tire. Depending on the tire positions, prior art air pressure gauges may be hard to read. Devices that extend the valve stem may influence the balance of the wheel.
Therefore a need existed to provide an air pressure gauge assembly mounted to a valve stem that has the capability of inflating and deflating the tire through the gauge itself, that not only continuously displays the tire pressure but is easy to read, that also may be able to indicate a warning for lower than normal air pressure, and therefore eliminates the use of an external handheld air pressure gauge.
A further need existed to provide an air pressure gauge assembly mounted to a valve stem that is relatively compact, light weight, and extends the valve stem relatively little to avoid curb contact and interference with the wheel balance.
A still further need existed to provide an air pressure gauge assembly mounted permanently to the wheel rim of a vehicle that does not interfere with the tire valve stem, that continuously displays the tire pressure in an easy to read way, and that may also be capable of indicating a warning for lower than normal air pressure.
A still further need existed to provide an air pressure gauge assembly that is able to withstand substantial impact and to seal the tire if the housing thereof is accidentally broken off or fractured.
A still further need existed to provide an air pressure gauge assembly that does not cause a problem when exchanging tires and/or the valve stem.
A still further need existed to provide an air pressure gauge that is sturdy enough to withstand the centrifugal forces of the rotating tire.
A still further need existed to provide an air pressure gauge that is relatively inexpensive, reliable, and of little or no maintenance.